From: Matthias Kaehlcke <mka@chromium.org> To: Alasdair Kergon <agk@redhat.com>, Mike Snitzer <snitzer@kernel.org>, Kees Cook <keescook@chromium.org>, James Morris <jmorris@namei.org>, "Serge E . Hallyn" <serge@hallyn.com> Cc: linux-security-module@vger.kernel.org, linux-raid@vger.kernel.org, Song Liu <song@kernel.org>, Milan Broz <gmazyland@gmail.com>, dm-devel@redhat.com, Douglas Anderson <dianders@chromium.org>, linux-kernel@vger.kernel.org, Matthias Kaehlcke <mka@chromium.org> Subject: [PATCH v7 1/3] dm: Add verity helpers for LoadPin Date: Mon, 27 Jun 2022 08:35:24 -0700 [thread overview] Message-ID: <20220627083512.v7.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> (raw) In-Reply-To: <20220627153526.3750341-1-mka@chromium.org> LoadPin limits loading of kernel modules, firmware and certain other files to a 'pinned' file system (typically a read-only rootfs). To provide more flexibility LoadPin is being extended to also allow loading these files from trusted dm-verity devices. For that purpose LoadPin can be provided with a list of verity root digests that it should consider as trusted. Add a bunch of helpers to allow LoadPin to check whether a DM device is a trusted verity device. The new functions broadly fall in two categories: those that need access to verity internals (like the root digest), and the 'glue' between LoadPin and verity. The new file dm-verity-loadpin.c contains the glue functions. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Acked-by: Kees Cook <keescook@chromium.org> --- Changes in v7: - rebased on v5.19-rc4 Changes in v6: - s/loadpin_trusted_verity_root_digests/dm_verity_loadpin_trusted_root_digests/ - s/trusted_root_digest/dm_verity_loadpin_trusted_root_digest/ - removed unnecessary symbol exports Changes in v5: - changed dm_verity_loadpin_is_sb_trusted() to dm_verity_loadpin_is_bdev_trusted() - bumped version number to 1.8.1 - deleted bad semicolon in declaration of stub for dm_verity_loadpin_is_bdev_trusted() - added 'Acked-by' tag from Kees Changes in v4: - a trusted verity device must have a single target of type 'verity' - share list of verity digests with loadpin, deleted dm_verity_loadpin_set_trusted_root_digests() - dm_verity_loadpin_is_md_trusted() is now dm_verity_loadpin_is_sb_trusted(), it receives a super_block instead of mapped_device. Updated kernel doc. - changed struct trusted_root_digest to have an unsized u8 array instead of a pointer - extend 'dm-verity-objs' instead of 'dm-mod-objs' Changes in v3: - none Changes in v2: - none drivers/md/Makefile | 6 +++ drivers/md/dm-verity-loadpin.c | 74 +++++++++++++++++++++++++++++++ drivers/md/dm-verity-target.c | 33 +++++++++++++- drivers/md/dm-verity.h | 4 ++ include/linux/dm-verity-loadpin.h | 27 +++++++++++ 5 files changed, 143 insertions(+), 1 deletion(-) create mode 100644 drivers/md/dm-verity-loadpin.c create mode 100644 include/linux/dm-verity-loadpin.h diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 0454b0885b01..71771901c823 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -108,6 +108,12 @@ ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y) dm-verity-objs += dm-verity-verify-sig.o endif +ifeq ($(CONFIG_DM_VERITY),y) +ifeq ($(CONFIG_SECURITY_LOADPIN),y) +dm-verity-objs += dm-verity-loadpin.o +endif +endif + ifeq ($(CONFIG_DM_AUDIT),y) dm-mod-objs += dm-audit.o endif diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c new file mode 100644 index 000000000000..10c18bc1652c --- /dev/null +++ b/drivers/md/dm-verity-loadpin.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/list.h> +#include <linux/kernel.h> +#include <linux/dm-verity-loadpin.h> + +#include "dm.h" +#include "dm-verity.h" + +#define DM_MSG_PREFIX "verity-loadpin" + +LIST_HEAD(dm_verity_loadpin_trusted_root_digests); + +static bool is_trusted_verity_target(struct dm_target *ti) +{ + u8 *root_digest; + unsigned int digest_size; + struct dm_verity_loadpin_trusted_root_digest *trd; + bool trusted = false; + + if (!dm_is_verity_target(ti)) + return false; + + if (dm_verity_get_root_digest(ti, &root_digest, &digest_size)) + return false; + + list_for_each_entry(trd, &dm_verity_loadpin_trusted_root_digests, node) { + if ((trd->len == digest_size) && + !memcmp(trd->data, root_digest, digest_size)) { + trusted = true; + break; + } + } + + kfree(root_digest); + + return trusted; +} + +/* + * Determines whether the file system of a superblock is located on + * a verity device that is trusted by LoadPin. + */ +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + struct mapped_device *md; + struct dm_table *table; + struct dm_target *ti; + int srcu_idx; + bool trusted = false; + + if (list_empty(&dm_verity_loadpin_trusted_root_digests)) + return false; + + md = dm_get_md(bdev->bd_dev); + if (!md) + return false; + + table = dm_get_live_table(md, &srcu_idx); + + if (dm_table_get_num_targets(table) != 1) + goto out; + + ti = dm_table_get_target(table, 0); + + if (is_trusted_verity_target(ti)) + trusted = true; + +out: + dm_put_live_table(md, srcu_idx); + dm_put(md); + + return trusted; +} diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index d6dbd47492a8..e5a01e2f96e9 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -19,6 +19,7 @@ #include <linux/module.h> #include <linux/reboot.h> #include <linux/scatterlist.h> +#include <linux/string.h> #define DM_MSG_PREFIX "verity" @@ -1310,10 +1311,40 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) return r; } +/* + * Check whether a DM target is a verity target. + */ +bool dm_is_verity_target(struct dm_target *ti) +{ + return ti->type->module == THIS_MODULE; +} + +/* + * Get the root digest of a verity target. + * + * Returns a copy of the root digest, the caller is responsible for + * freeing the memory of the digest. + */ +int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size) +{ + struct dm_verity *v = ti->private; + + if (!dm_is_verity_target(ti)) + return -EINVAL; + + *root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL); + if (*root_digest == NULL) + return -ENOMEM; + + *digest_size = v->digest_size; + + return 0; +} + static struct target_type verity_target = { .name = "verity", .features = DM_TARGET_IMMUTABLE, - .version = {1, 8, 0}, + .version = {1, 8, 1}, .module = THIS_MODULE, .ctr = verity_ctr, .dtr = verity_dtr, diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 4e769d13473a..c832cc3e3d24 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -129,4 +129,8 @@ extern int verity_hash(struct dm_verity *v, struct ahash_request *req, extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, sector_t block, u8 *digest, bool *is_zero); +extern bool dm_is_verity_target(struct dm_target *ti); +extern int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, + unsigned int *digest_size); + #endif /* DM_VERITY_H */ diff --git a/include/linux/dm-verity-loadpin.h b/include/linux/dm-verity-loadpin.h new file mode 100644 index 000000000000..fb695ecaa5d5 --- /dev/null +++ b/include/linux/dm-verity-loadpin.h @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __LINUX_DM_VERITY_LOADPIN_H +#define __LINUX_DM_VERITY_LOADPIN_H + +#include <linux/list.h> + +struct block_device; + +extern struct list_head dm_verity_loadpin_trusted_root_digests; + +struct dm_verity_loadpin_trusted_root_digest { + struct list_head node; + unsigned int len; + u8 data[]; +}; + +#if IS_ENABLED(CONFIG_SECURITY_LOADPIN) && IS_BUILTIN(CONFIG_DM_VERITY) +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev); +#else +static inline bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + return false; +} +#endif + +#endif /* __LINUX_DM_VERITY_LOADPIN_H */ -- 2.37.0.rc0.161.g10f37bed90-goog
WARNING: multiple messages have this Message-ID (diff)
From: Matthias Kaehlcke <mka@chromium.org> To: Alasdair Kergon <agk@redhat.com>, Mike Snitzer <snitzer@kernel.org>, Kees Cook <keescook@chromium.org>, James Morris <jmorris@namei.org>, "Serge E . Hallyn" <serge@hallyn.com> Cc: linux-kernel@vger.kernel.org, dm-devel@redhat.com, Douglas Anderson <dianders@chromium.org>, linux-raid@vger.kernel.org, Song Liu <song@kernel.org>, linux-security-module@vger.kernel.org, Matthias Kaehlcke <mka@chromium.org>, Milan Broz <gmazyland@gmail.com> Subject: [dm-devel] [PATCH v7 1/3] dm: Add verity helpers for LoadPin Date: Mon, 27 Jun 2022 08:35:24 -0700 [thread overview] Message-ID: <20220627083512.v7.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> (raw) In-Reply-To: <20220627153526.3750341-1-mka@chromium.org> LoadPin limits loading of kernel modules, firmware and certain other files to a 'pinned' file system (typically a read-only rootfs). To provide more flexibility LoadPin is being extended to also allow loading these files from trusted dm-verity devices. For that purpose LoadPin can be provided with a list of verity root digests that it should consider as trusted. Add a bunch of helpers to allow LoadPin to check whether a DM device is a trusted verity device. The new functions broadly fall in two categories: those that need access to verity internals (like the root digest), and the 'glue' between LoadPin and verity. The new file dm-verity-loadpin.c contains the glue functions. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Acked-by: Kees Cook <keescook@chromium.org> --- Changes in v7: - rebased on v5.19-rc4 Changes in v6: - s/loadpin_trusted_verity_root_digests/dm_verity_loadpin_trusted_root_digests/ - s/trusted_root_digest/dm_verity_loadpin_trusted_root_digest/ - removed unnecessary symbol exports Changes in v5: - changed dm_verity_loadpin_is_sb_trusted() to dm_verity_loadpin_is_bdev_trusted() - bumped version number to 1.8.1 - deleted bad semicolon in declaration of stub for dm_verity_loadpin_is_bdev_trusted() - added 'Acked-by' tag from Kees Changes in v4: - a trusted verity device must have a single target of type 'verity' - share list of verity digests with loadpin, deleted dm_verity_loadpin_set_trusted_root_digests() - dm_verity_loadpin_is_md_trusted() is now dm_verity_loadpin_is_sb_trusted(), it receives a super_block instead of mapped_device. Updated kernel doc. - changed struct trusted_root_digest to have an unsized u8 array instead of a pointer - extend 'dm-verity-objs' instead of 'dm-mod-objs' Changes in v3: - none Changes in v2: - none drivers/md/Makefile | 6 +++ drivers/md/dm-verity-loadpin.c | 74 +++++++++++++++++++++++++++++++ drivers/md/dm-verity-target.c | 33 +++++++++++++- drivers/md/dm-verity.h | 4 ++ include/linux/dm-verity-loadpin.h | 27 +++++++++++ 5 files changed, 143 insertions(+), 1 deletion(-) create mode 100644 drivers/md/dm-verity-loadpin.c create mode 100644 include/linux/dm-verity-loadpin.h diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 0454b0885b01..71771901c823 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -108,6 +108,12 @@ ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y) dm-verity-objs += dm-verity-verify-sig.o endif +ifeq ($(CONFIG_DM_VERITY),y) +ifeq ($(CONFIG_SECURITY_LOADPIN),y) +dm-verity-objs += dm-verity-loadpin.o +endif +endif + ifeq ($(CONFIG_DM_AUDIT),y) dm-mod-objs += dm-audit.o endif diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c new file mode 100644 index 000000000000..10c18bc1652c --- /dev/null +++ b/drivers/md/dm-verity-loadpin.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/list.h> +#include <linux/kernel.h> +#include <linux/dm-verity-loadpin.h> + +#include "dm.h" +#include "dm-verity.h" + +#define DM_MSG_PREFIX "verity-loadpin" + +LIST_HEAD(dm_verity_loadpin_trusted_root_digests); + +static bool is_trusted_verity_target(struct dm_target *ti) +{ + u8 *root_digest; + unsigned int digest_size; + struct dm_verity_loadpin_trusted_root_digest *trd; + bool trusted = false; + + if (!dm_is_verity_target(ti)) + return false; + + if (dm_verity_get_root_digest(ti, &root_digest, &digest_size)) + return false; + + list_for_each_entry(trd, &dm_verity_loadpin_trusted_root_digests, node) { + if ((trd->len == digest_size) && + !memcmp(trd->data, root_digest, digest_size)) { + trusted = true; + break; + } + } + + kfree(root_digest); + + return trusted; +} + +/* + * Determines whether the file system of a superblock is located on + * a verity device that is trusted by LoadPin. + */ +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + struct mapped_device *md; + struct dm_table *table; + struct dm_target *ti; + int srcu_idx; + bool trusted = false; + + if (list_empty(&dm_verity_loadpin_trusted_root_digests)) + return false; + + md = dm_get_md(bdev->bd_dev); + if (!md) + return false; + + table = dm_get_live_table(md, &srcu_idx); + + if (dm_table_get_num_targets(table) != 1) + goto out; + + ti = dm_table_get_target(table, 0); + + if (is_trusted_verity_target(ti)) + trusted = true; + +out: + dm_put_live_table(md, srcu_idx); + dm_put(md); + + return trusted; +} diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index d6dbd47492a8..e5a01e2f96e9 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -19,6 +19,7 @@ #include <linux/module.h> #include <linux/reboot.h> #include <linux/scatterlist.h> +#include <linux/string.h> #define DM_MSG_PREFIX "verity" @@ -1310,10 +1311,40 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) return r; } +/* + * Check whether a DM target is a verity target. + */ +bool dm_is_verity_target(struct dm_target *ti) +{ + return ti->type->module == THIS_MODULE; +} + +/* + * Get the root digest of a verity target. + * + * Returns a copy of the root digest, the caller is responsible for + * freeing the memory of the digest. + */ +int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size) +{ + struct dm_verity *v = ti->private; + + if (!dm_is_verity_target(ti)) + return -EINVAL; + + *root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL); + if (*root_digest == NULL) + return -ENOMEM; + + *digest_size = v->digest_size; + + return 0; +} + static struct target_type verity_target = { .name = "verity", .features = DM_TARGET_IMMUTABLE, - .version = {1, 8, 0}, + .version = {1, 8, 1}, .module = THIS_MODULE, .ctr = verity_ctr, .dtr = verity_dtr, diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 4e769d13473a..c832cc3e3d24 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -129,4 +129,8 @@ extern int verity_hash(struct dm_verity *v, struct ahash_request *req, extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, sector_t block, u8 *digest, bool *is_zero); +extern bool dm_is_verity_target(struct dm_target *ti); +extern int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, + unsigned int *digest_size); + #endif /* DM_VERITY_H */ diff --git a/include/linux/dm-verity-loadpin.h b/include/linux/dm-verity-loadpin.h new file mode 100644 index 000000000000..fb695ecaa5d5 --- /dev/null +++ b/include/linux/dm-verity-loadpin.h @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __LINUX_DM_VERITY_LOADPIN_H +#define __LINUX_DM_VERITY_LOADPIN_H + +#include <linux/list.h> + +struct block_device; + +extern struct list_head dm_verity_loadpin_trusted_root_digests; + +struct dm_verity_loadpin_trusted_root_digest { + struct list_head node; + unsigned int len; + u8 data[]; +}; + +#if IS_ENABLED(CONFIG_SECURITY_LOADPIN) && IS_BUILTIN(CONFIG_DM_VERITY) +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev); +#else +static inline bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + return false; +} +#endif + +#endif /* __LINUX_DM_VERITY_LOADPIN_H */ -- 2.37.0.rc0.161.g10f37bed90-goog -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2022-06-27 15:35 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-27 15:35 [PATCH v7 0/3] LoadPin: Enable loading from trusted dm-verity devices Matthias Kaehlcke 2022-06-27 15:35 ` [dm-devel] " Matthias Kaehlcke 2022-06-27 15:35 ` Matthias Kaehlcke [this message] 2022-06-27 15:35 ` [dm-devel] [PATCH v7 1/3] dm: Add verity helpers for LoadPin Matthias Kaehlcke 2022-07-06 15:06 ` Mike Snitzer 2022-07-06 15:06 ` [dm-devel] " Mike Snitzer 2022-06-27 15:35 ` [PATCH v7 2/3] LoadPin: Enable loading from trusted dm-verity devices Matthias Kaehlcke 2022-06-27 15:35 ` [dm-devel] " Matthias Kaehlcke 2022-07-06 15:08 ` Mike Snitzer 2022-07-06 15:08 ` [dm-devel] " Mike Snitzer 2022-06-27 15:35 ` [PATCH v7 3/3] dm: verity-loadpin: Use CONFIG_SECURITY_LOADPIN_VERITY for conditional compilation Matthias Kaehlcke 2022-06-27 15:35 ` [dm-devel] " Matthias Kaehlcke 2022-07-06 15:09 ` Mike Snitzer 2022-07-06 15:09 ` [dm-devel] " Mike Snitzer 2022-07-06 15:11 ` [PATCH v7 0/3] LoadPin: Enable loading from trusted dm-verity devices Mike Snitzer 2022-07-06 15:11 ` [dm-devel] " Mike Snitzer 2022-07-07 3:58 ` Kees Cook 2022-07-07 3:58 ` Kees Cook 2022-07-08 17:47 ` Kees Cook 2022-07-08 17:47 ` [dm-devel] " Kees Cook
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